League-Adjusted Strikeouts

One of the pleasures of baseball lies in the ease of its translation. Though the game certainly has had its distinct eras, an evolution of rules and enforcement and training, the consistency of baseball is unrivaled by the like of football or basketball. Baseball has never had to struggle with a reconception of its most basic elements, like what a catch and a foul are; certainly, the game has changed, but in the past hundred years it’s at least recognizable.

But the statistical environment of different eras do obviously fluctuate, and we as fans struggle to encompass this. Not that we aren’t aware of it; we know a 3.00 ERA in 1968 means something very different than that same mark in 1999. But it requires an annoying internalized equation, a consistent demand to double the numbers and add 30. It leads us to rough approximations at best, and often lulls us to the siren’s song of the Fun Fact over the untranslated truth.

This isn’t intellectual dishonesty. Rate stats are all well and good, but nothing captures the heart like a milestone. Numbers like 3,000 hits and 300 wins and 500 home runs still pull at us, despite the fact that some of those lights have receded from or washed up on the shore. Even the benchmarks of our rate stats require constant supervision: the career K/9 of Nolan Ryan, for example, is 9.55, a strong number, and one just shy of James Shields’ 2015 season.

We have some statistics that deal with this. Weighted on-base average (wOBA) and Baseball Prospectus’ True Average both seek to approximate a player’s offensive contribution and condense it into a single number, consistent across eras, and do so admirably. But neither is particularly intuitive: say a batter has a .330 wOBA. Is that average? If you’ve spent your time dealing with steroid era numbers, it’ll look low. One person could come away happier with a number than another person. Statistics like wRC+ and ERA+ remove this doubt by adjusting to 100: 102 is two percent higher than average, 98 is two percent lower. It’s far easier to visualize. But certain statistics have been left out in the cold.

If there’s a single defining feature of the modern, post-steroid game of baseball, it’s not runs allowed or home runs hit. It’s strikeouts, which continue to climb at climate change-level rates. At a glance, the all-time K/9 reveals that five of the top six strikeout pitchers of all time will pitch in 2016. You have to go all the way to 46th place to find someone who pitched before the mid-80s (Dick Radatz), and to get there you have to pass by such luminaries as Marlins middle reliever Mike Dunn and journeyman Michael Gonzalez. Clearly, the numbers we use to define greatness have gotten away from us a little.

The solution: league-adjusted strikeout rate. It’s nothing fancy:

(strikeouts / batters faced) / (league strikeouts / league batters faced) * 100

A pitcher who struck out the exact same ratio of batters as the league he played in that year would score 100; twice as many would score 200, half as many 50. Higher is, assuming you’re rooting for the pitcher, better.

Seasonal K%+ Scores

What we can learn from this:

Dazzy Vance is the greatest starting strikeout pitcher of all time.

In his greatest strikeout season, 1924, Vance struck out 7.65 batters per nine innings. That number was surpassed by 40 qualified pitchers in 2015, including one Rick Porcello. But in that year, the remainder of the National League struck out a mere 2.63 batters per nine, and actually walked more batters than they dismissed. That’s amazing enough, but what truly astounds is how often his name shows up. While many other pitchers had a year or two at peak velocity, Vance’s six-year run (1923-1928) all rank in the top 12 seasons among starters all-time. It was a different time, but Vance owned an era in a way that doesn’t get the credit that Cy Young and Christy Mathewson received.

The seventies belonged to Nolan Ryan.

This is not a surprise, although Ryan rather surprisingly never had an elite strikeout season in the 1995 Randy Johnson mold. You have to go through five Ryan years to get to the next guy, teammate Frank Tanana, who serves as a pretty good example of how hard it is to make the top of the list multiple times. It’s fun to see 1989 Nolan Ryan and 1973 Nolan Ryan right next to each other.

The fifties didn’t really belong to anyone.

Actually, they belonged to Herb Score, who owns two of the only three appearances of the decade in the K%+ top 100. But with his career cut tragically short, and Koufax spending much of the fifties still finding his bearings, there’s just no other strikeout pitchers that dominate the era.

Johnny Vander Meer wasn’t just a two-game wonder; he was a two-year wonder.

The long-time Reds starter is basically known for one fun fact: he’s the only pitcher to throw back-to-back no hitters (and perhaps always will be). But he was pretty formidable for a whole season in 1941, years after his historic feat. The top of the starter list is actually surprisingly light on non-Hall of Famers, given how quickly the fastball can go; he and Herb Score (whose career was derailed by injuries) are the only two outsiders in the top 20.

Kirk Rueter started 13 years in the major leagues somehow.

Rueter was one of those guys pressed into service as a youngster, one who never had anything to work with. (His highest adjusted strikeout rate was 81.) Perhaps only his perfect 8-0 record got him a second season, but he wound up with four playoff berths. But despite plying his trade in the heart of the steroid era, despite wielding an arsenal as threatening as a pitching machine, he never sank below 0.7 fWAR in a season. Until his last, when he pitched 107.1 innings and struck out 25 batters – five of them opposing pitchers.

Relievers who strike out a lot of batters aren’t the stereotypical wild men.

The iconic fireballing reliever, perhaps embedded into our consciousness by Ricky Vaughn and Mitch Williams, doesn’t hold true. While few of the names near the top of the list could be called control artists, neither do we find many Marmols. In fact, perhaps surprisingly given the nature and volatility of relievers, what we find are many famous players, members of the Hall of Fame or at least Hall of Very Great, with decent if not amazing walk rates. A fun comparison is Bryan Harvey, whose 1989 and 1991 seasons show up near each other – the former combined with a 6.7 BB/9, the latter with a 1.9 BB/9.

The great strikeout relievers of our time are great in any time.

Despite the inflated strikeout numbers of the modern era, the greatness of Aroldis Chapman, Craig Kimbrel and Kenley Jansen hold up pretty well. The dominant relievers of our era really are dominant. But Eric Gagne’s one majestic season still edges them, as easy as it is to forget now.

Rob Dibble could have been a Hall of Famer.

In the modern era (1988 forward), Dibble ended his career at age 31 with 12.9 fWAR, good for 20th among relievers and tied with Craig Kimbrel in almost the same amount of career innings. Throw out his two failed comebacks, which cost his value a win apiece, and he leaps up into a tie for 12th, among pitchers who threw at least twice as many career innings. His four great seasons all rank in the top 20. Whether or not his fastball flew too close to the sun, it’s a warning for fans of the modern closers: relievers just don’t age like they used to.

Ryne Duren’s legacy deserves another look.

One of the tendencies we have in baseball and human nature is that we focus on the most glaring characteristic in a person. Rarely was this more on display than with Duren, whose near-blindness and shaded coke-bottle glasses only fed into the fame of his terrible wildness. Perhaps the fear of an uncontrollable, half-blind (and two-thirds drunk) reliever throwing high-90s fastball did the job of intimidating and disconcerting batters, but it also led to the pitcher’s own caricaturization. Forever battling against expectations, potential and sobriety, Duren was shipped out at the first sign of weakness, and ultimately the man cleaned himself up and became a prolific speaker for alcoholics in his post-playing days. But despite near-anonymity now, this stat shows that at his peak, he was quite effective despite the walks, and deserving of at least as much lasting notoriety as Mitch Williams.

Ted Wingfield’s 1927 season is impossible to conceive.

If not for this statistic, Wingfield would be utterly forgotten, a swingman for a few years in the Roaring Twenties with a poor ERA on last-place teams. But his final encore at the age of 27 is the stuff of numeric legends: he faced 346 batters and struck out exactly one of them. It took him four months to get it, in fact, picking it up in long relief on August 10, striking out Max Bishop. His eight consecutive starts without a strikeout is a record that might stand the test of time, and only retirement kept it from going higher.

The best – and the worst – strikeout seasons in history failed to make the cut.

To qualify for the starter list a pitcher had to go 100 innings, and to qualify for the reliever list, a pitcher had to be predominantly a reliever. This cut off outliers on both ends of the spectrum. On the low end, we lose Aaron Cook’s final season, which was Kirk Rueter version 1.1. (The two started the same number of games, but Cook missed the innings cut because he wasn’t as good.) On the high end, we lose Bob Feller’s rookie season, where he struck out 70 batters in 54 innings as a starter, all before becoming a legal adult. Only three pitchers in the league that year managed even half his 11.03 K/9.

Career K%+ Scores

Included below are a list of career K%+ scores for the top 100 and bottom 10 pitchers in baseball history who have faced at least 1,000 batters in their career. Please note that career totals are not meant to be compared against each other the way that season totals can be. There are a couple of reasons for this. First, since K% declines with age, pitchers who were too ineffective to last into their thirties, or who have been prevented from reaching them by the present tense, will have inflated numbers. And since we’re working with a list of numbers with different denominators, eras with high league-average strikeout rates will see generally flatter bell curves than strikeout-depressed eras. That’s why so many of the scores in the 130s and 70s belong to the deadball era.

The data is yours to look at and manipulate: if you want to start in more modern times, you can cut down the date ranges, or perhaps change the game started cutoff for starters versus relievers. This isn’t a predictive stat, so you can have fun with the data and decide how you want it to mean to you.

The K%+ statistic doesn’t really tell us anything new. That doesn’t mean it’s not useful; calculators don’t tell us anything new, but they make the math easier. Think of this statistic as shorthand, a means of reminding us that each pitcher existed in his own time and conditions. And that Dazzy Vance was really, really amazing.

References & Resources

• Tony Blengino, The Hardball Times Baseball Annual 2015, “The Power Pitcher Championship Belt”